The invention set forth in this specification relates to what may be referred to as a flow control structure. Such a structure is primarily intended to be utilized as a compensating emitter in agricultural applications. Such structures are intended to discharge a substantially uniform quantity of water as required in agricultural watering or irrigation regardless of whether or not there are changes in the pressure of water supplied to the emitter from a principal distribution conduit. The structures within the scope of the invention can obviously be employed for other than agricultural uses wherever it is desired to dispense a substantially uniform quantity of liquid from a conduit in which liquid may be at various different pressures.
An indication such as the preceding of the nature of flow control structures of the present invention unfortunately does little to clearly delineate the reasons as to why the flow control structures of the invention are important and significant. These reasons primarily relate to agricultural watering or irrigation procedures. Within comparatively recent times the distribution of water in order to promote plant growth has undergone significant changes. Increasingly it has been recognized that it is most economical and effective to distribute measured amounts of water to individual plants or small areas through appropriate conduits and to emit such quantities of water at a limited control rate.
As an elongated conduit is used in distributing water the pressure of the water will vary at various points along the length of the conduit. In part, this is due to the usual considerations relative to fluid flow. Frequently such variation will be a consequence of a conduit extending at different elevations. Thus, for example, when a distribution conduit goes up and down hill it is to be expected that the pressure of water within the conduit will vary at various points along the length of the conduit. In addition, when such a conduit is used to distribute water at various locations along its length, the pressures at various distribution points will also be influenced by the amount of liquid emitted from the conduit at such points.
These factors are considered to make it desirable to utilize in agricultural watering or irrigation flow control structures which will dispense controlled, substantially uniform quantities of water, regardless of the internal pressure within a distribution conduit as indicated in the preceding discussion. Prior efforts at providing such structures are considered to have been substantially unacceptable for any one of a variety of reasons. It is not considered that an understanding of this invention requires a detailed discussion relative to all of such reasons. A number of factors including costs, effectiveness, ease of installation, reliability and the like all relate to the acceptability of a flow control structure.